Neuropsychiatric manifestations are increasingly recognized to be major contributors to the morbidity of lupus patients. We have developed a model for cognitive impairment and behavioral alteration in lupus patients, based on our observation that our subset of anti-DNA antibodies cross-reacts with a 5 amino acid sequence present in the extracellular domain of the NR2A and NR2B subunits of the N-methyl-D-aspartate receptor (NMDAR). These antibodies are present in serum, cerebrospinal fluid and brain tissue of lupus patients. When antibodies with this specificity, whether of mouse or human origin, breach the blood-brain barrier and access brain tissue, they mediate neuronal death. When bacterial lipopolysaccharide is used to compromise the blood-brain barrier, the antibodies damage neurons in the hippocampus and cause memory impairment. When epinephrine is used to compromise the blood-brain barrier, the antibodies damage neurons in the amygdala and cause a behavioral deficit. We now propose to determine: 1) whether complement components and Fc receptor-bearing cells contribute to neuronal injury or whether injury is in purely a consequence of NMDAR modulation by antibody;2) whether we can identify monoclonal anti-NMDAR antibodies with distinct epitope specificity and distinct neurotoxic or neuroprotective potential;and 3) whether we can purify from human lupus serum antibodies that bind distinct sites on the NMDAR and alter neuronal function in unique ways. We will use human monoclonal antibodies derived from a combinatorial library made from splenic B cells of a lupus patient and antibodies cloned from peripheral blood B cells of lupus patients by single cell PCR, as well as lupus serum in these studies. Neurologic assessments will be made by electrophysiologic analyses and cognitive and behavioral testing will be performed in mice exposed to antibody in vivo. This application represents a multidisciplinary approach to build on a novel model for neuropsychiatric manifestations of lupus and a novel paradigm for antibody-mediated changes in cognition and behavior.